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U.S. STEEL DUQUESNE WORKS HAER No. PA-115 (Page 167) track by a dinky to the charging floor of the furnace building and deposited alongside one of the furnaces. A Wellman-Seaver charging machine running on wide gauge track adjacent to the boxes and equipped with a hydraulically operated arm or "peel" picked the boxes up in sequence and overturned them into the furnace hearth through its water-cooled charging doors. Limestone was charged first, followed by iron ore and finally the scrap. The entire mass was heated for approximately two hours, or until the scrap was white hot and slightly fused, by burning natural gas mixed with combustion air over it. During the period in which the furnace operated, waste gas and combustion air were passed alternatively through the furnace's regenerative heating chambers every twenty minutes. Constructed of brick checkerwork, the regenerative chambers were located below the structural charging floor and away from the furnace. When the initial charge was ready, a ladle full of molten pig iron, drawn from the mixer at the Bessemer plant, was transported by an E.O.T. crane and charged into the furnace through a spout inserted into the charging door. Soon after the molten iron had been charged, a reaction occurred in which almost all of the silicon, manganese, phosphorus, sulphur, and part of the carbon was eliminated. All of these materials except the carbon, which escaped as carbon monoxide and caused an agitation of the bath, became part of the slag. During the next two or three hours, about 80 percent of this slag flushed into a slag pot through a notch located in the back of the furnace. The iron ore then entered a three to four hour period known as the "ore boil" during which it reacted with the carbon. Then, for approximately two or three hours carbon dioxide emitted from the limestone as it was being decomposed by the heat bubbled through the bath and exposed part of the metal to the flame, thus oxidizing it. Known as the "lime boil," this activity completed the purification begun by the ore reaction and left the carbon content of the bath somewhat greater than that at which the metal was to be tapped. If, after a sample of the molten metal was taken, it was determined that the carbon content was too high or too low, more pig iron or iron ore was added. In any case, after about another hour the carbon content was reduced to the proper level for tapping. The temperature of the bath at tapping was in the neighborhood of 3000° F., varying according to the composition and grade of the steel. Tapping began with the digging out of the clay-loam plug and dolomite used to seal the tap hole before the furnace was charged. Molten steel escaped from the tapping hole, which was located at the lowest level of the hearth, into a teeming ladle through a removable spout. The ladle was set on a stand below
U.S. STEEL DUQUESNE WORKS HAER No. PA-115 (Page 168) the tapping hole in a shallow ladle pit by an E.O.T. crane. Owing to the position of the tap hole, the greater portion of the steel flowed out of the furnace before slag appeared in the spout, thus allowing time for the addition of alloying, recarburizing, and deoxidizing materials into the ladle as it filled up with molten steel. The remaining slag was directed into an adjacent cinder pot through a spout attached to the ladle after a sufficient depth of slag covered the steel for protective purposes. As soon as the slag removal was complete, the ladle was removed from its supporting stand and conveyed by an E.O.T. crane to a position over the ingot moulds located next to the teeming platform, while the slag was dumped in the cinder yard. After teeming was complete, the ladle was conveyed to the skull cracker where a large steel ball attached to a E.O.T. crane knocked solidified steel off the lip and sides of the teeming ladle in much the same manner as a wrecking ball is utilized to demolish a building. 2 Duquesne dramatically expanded its open hearth facilities in the years immediately following the construction of Open Hearth Number One. Between 1902 and 1907, eight furnaces (two 50-ton capacity and six 60-ton capacity) were added to Open Hearth Number One's facility. In 1908, Bessemer production was abandoned and construction of a new basic open hearth plant (Open Hearth Number Two) began on the site of the Bessemer/blooming mill complex. The new plant, which was built along the same lines as Open Hearth Number One, was eguipped with twelve 60-ton capacity stationary furnaces. In addition, a mixer building for each plant, a gas producer facility, and a calcining plant was added. A 300 ton capacity mixer was installed in each mixer building. The gas producer building, which contained 32 furnaces, was built between the furnace buildings of Open Hearth Number One and Number Two. It generated gaseous fuel for each open hearth plant by forcing air and steam up through a bed of coal located in the hearth of the refractory brick-lined furnaces. The resulting carbon monoxide given off by the incandescent coal was directed through flues to the burners of the open hearth furnaces. The calcining plant contained cupolas which were used for roasting dolomite. The calcined dolomite was subsequently used to repair the banks and bottoms of the open hearth furnaces. 3 Between 1908 and the shutdown of open hearth steelmaking at Duquesne in 1965, there were a number of significant changes to the system. The installation of coke oven gas lines from the Clairton Works in 1918, for example, gave the open hearth furnaces the added capability of utilizing another fuel besides natural and producer gas. The period also witnessed a number of furnace rebuilds which steadily increased furnace capacity. By
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Installation Date: 1955. U.S. STEEL
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cooling tower has a capacity of 190
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